PENDLETON, Ore. (AP) — As a child in Pendleton, Nicole Nicassio-Hiskey had every pet she could slip past her mother. Turtles, rats, dogs and cats all roamed the Nicassio household.

As the senior marine animal keeper at the Oregon Zoo, Nicassio-Hiskey’s animal interactions have only broadened with age. She works with sea lions, polar bears, tigers and leopards in the Portland zoo.

“I knew what I wanted to do as a kid,” Nicassio-Hiskey said. “We didn’t have a zoo or aquarium growing up in Pendleton, so I would go to the library and soak everything up I could.”

After graduating from Oregon State University in 1993, Nicassio-Hiskey worked with Keiko the orca at the Oregon Coast Aquarium and in the city of Anchorage, Alaska’s animal control department before landing at the Oregon Zoo.

After two decades of training all types of species, the zookeeper wrote “Beyond Squeaky Toys” with co-author Cinthia Mitchell about creating enriching environments for dogs and cats.

“We figured this out long ago with exotic animals but we have kind of gone backward with dogs and cats,” Nicassio-Hiskey said of animal training techniques. “A hundred years ago, zoos had cages with lions pacing back and forth, then we moved toward a more natural environment, then an enriching environment.”

In her job, Nicassio-Hiskey creates puzzles for the polar bears to work through to get a piece of meat and places swift little fish in the water for them to catch.

She explains in her book that domestic animals also want something to do when they are home during the day. If they can’t be out herding sheep, filling an empty water bottle with kibble or placing a tennis ball in a sock can do the trick.

Nicassio-Hiskey may have graduated from training Pendleton pet rats to exotic animal celebrities, but she says the concept is the same. Animals, like humans, respond to positive reinforcement and engaging environments.

“Dogs had jobs when they were first domesticated,” Nicassio-Hiskey said. “They’re like us. They feel fulfilled in jobs. We’ve gone from that to putting them in cute little outfits and having them sit around the house bored.”